Process for preparing-diketone compound and process for preparing metal complex thereof

ABSTRACT

Disclosed is a process for preparing 2,2,6,6-tetramethyl-3,5-heptanedione, comprising reacting a pivalic acid alkyl ester with pinacolone in the presence of an alkali metal alkoxide catalyst using a pivalic acid alkyl ester as a solvent but using no other solvent or reacting them in an amide type or urea type solvent in the presence of an alkali metal alkoxide catalyst. Also disclosed is a process for preparing a 2,2,6,6-tetramethyl-3,5-heptanesione metal complex using the 2,2,6,6-tetramethyl-3,5-heptanedione obtained by the above process. The process for preparing 2,2,6,6-tetramethyl-3,5-heptanedione is an industrially advantageous process in which an alkali metal alkoxide that is easy to handle can be used-as a catalyst for preparing 2,2,6,6-tetramethyl-3,5-heptanedione from a pivalic acid alkyl ester and pinacolone.

CROSS REFERENCES OF RELATED APPLICATION

This application is an application filed under 35 U.S.C. §111(a)claiming benefit pursuant to 35 U.S.C. §119(e) (1) of the filing date ofProvision Application 60/384,393 filed on Jun. 3, 2002 pursuant to 35U.S.C. §111(b).

FIELD OF THE INVENTION

The present invention relates to a process for preparing a β-diketonecompound that is useful as a ligand of a volatile organometallic complexused as, for example, a starting material of MOCVD (metal organicchemical vapor deposition), and more particularly to a process forpreparing 2,2,6,6-tetramethyl-3,5-heptanedione.

The present invention also relates to a process for preparing a2,2,6,6-tetramethyl-3,5-heptanedione metal complex using the2,2′,6,6-tetramethyl-3,5-heptanedione.

BACKGROUND OF THE INVENTION

As a process for the production of inorganic or metal thin films, MOCVDhas been widely applied, and as MOCVD materials, metal alkoxides,β-diketone complexes, etc. have been developed. Of these,2,2,6,6-tetramethyl-3,5-heptanedione is known to form volatile complexestogether with relatively many kinds of metals, but this compound has notbecome so widespread industrially because it is expensive.

A process using Claisen condensation is well known as a process forpreparing the 2,2,6,6-tetramethyl-3,5-heptanedione. For example, in J.Am. Chem. Soc., 66, 1220 (1944), ethyl pivalate is reacted withpinacolone (3,3-dimethyl-2-butanone, tert-butyl methyl ketone) using asodium amide catalyst to synthesize 2,2,6,6-tetramethyl-3,5-heptanedionein a yield of 28%. In this report, acylation reaction of methyl ketonewith an ester using sodium ethoxide is also described, and it isreported that the reactivity is inferior when a higher ester is used.

In J. Org. Chem., 27, 1036 (1962), methyl pivalate is reacted withpinacolohe using a sodium hydride catalyst to synthesize2,2,6,6-tetramethyl-3,5-heptanedione in a yield of 60 to 70%.

Other examples of the process for preparing2,2,6,6-tetramethyl-3,5-heptanedione using Claisen condensation reactionhave also been reported. In any of these processes, however, sodiumhydride or sodium amide that is difficult to handle similarly to themetallic sodium is used, and there resides a problem of safety.Moreover, safety countermeasures thereto are necessary, and hence, it isdifficult to use these processes industrially.

In addition to the above processes, a synthesis process using Grignardreaction of malonyl chloride with t-BuMgCl (t-Bu is a tert-butyl group)and a synthesis process using a reaction of malonyl chloride witht-BuCu(Li)SPh have been reported. In these processes, however, anextremely low temperature of about −70° C. is necessary, and handling isvery difficult. Thus, there are problems in the industrial practice.

As described above, any industrially advantageous process wherein2,2,6,6-tetramethyl-3,5-heptanedione can be prepared by simple and easyoperations at a low cost has been unknown so far, and furtherimprovement has been desired.

OBJECT OF THE INVENTION

It is an object of the present invention to provide an industriallyadvantageous process wherein a β-diketone compound represented by thefollowing formula (3) can be obtained.CR¹R²R³COCHR⁸COCR⁵R⁶R⁷   (3)wherein R¹ to R³ and R⁵ to R⁷ are each independently an alkyl group of 1to 3 carbon atoms, and R⁶ is hydrogen or an alkyl group of 1 to 4 carbonatoms.

Particularly, it is an object of the present invention to provide anindustrially advantageous process wherein2,2,6,6-tetramethyl-3,5-heptanedione can be obtained easily and at a lowcost.

More specifically, it is an object of the invention to provide a processwherein an alkali metal alkoxide catalyst can be used for the reactionof an ester compound represented by the formula (1):CR¹R²R³COOR⁴   (1)wherein R¹ to R³ are each independently an alkyl group of 1 to 3 carbonatoms, and R⁴ is an alkyl group,

-   -   with a ketone compound represented by the formula (2):        CR⁵R⁶R⁷COCH₂R⁸   (2)        wherein R⁵ to R⁷ are each independently an alkyl group of 1 to 3        carbon atoms, and R⁸ is hydrogen or an alkyl group of 1 to 4        carbon atoms,    -   to prepare the β-diketone compound represented by the formula        (3).

That is to say, it is an object of the invention to provide a processwherein an alkali metal alkoxide can be used as a catalyst for preparing2,2,6,6-tetramethyl-3,5-heptanedione from a pivalic acid alkyl ester andpinacolone which are starting materials.

It is another object of the invention to provide a process for preparinga 2,2,6,6-tetramethyl-3,5-heptanedione metal complex by reacting the2,2,6,6-tetramethyl-3,5-heptanedione prepared as above with a metalsalt.

The present inventors have earnestly studied to solve such problemsassociated with the prior art as described above, and as a result, theyhave found that 2,2,6,6-tetramethyl-3,5-heptanedione can be synthesizedin the presence of an alkali metal alkoxide catalyst that is easy tohandle by reacting a pivalic acid alkyl ester with pinacolone using apivalic acid alkyl ester as a solvent but using no other solvent in thebeginning of the reaction or by reacting them in an amide type or ureatype solvent. Based on the finding, the present invention has beenaccomplished.

Further, the present inventors have also found that by the reaction ofthe thus prepared 2,2,6,6-tetramethyl-3,5-heptanedione with a metalsalt, a 2,2,6,6-tetramethyl-3,5-heptanedione metal complex can bereadily obtained.

SUMMARY OF THE INVENTION

That is to say, the present invention is as follows.

[1] A process for preparing a β-diketone compound represented by thefollowing formula (3), comprising a step 1 of reacting an ester compoundrepresented by the following formula (1) with a ketone compoundrepresented by the following formula (2) in the presence of an alkalimetal alkoxide catalyst,CR¹R²R³COOR⁴   (1)wherein R¹ to R³ are each independently an alkyl group of 1 to 3 carbonatoms, and R⁴ is an alkyl group,CR⁵R⁶R⁷COCH₂R⁸   (2)wherein R⁵ to R⁷ are each independently an alkyl group of 1 to 3 carbonatoms, and R⁸ is hydrogen or an alkyl group of 1 to 4 carbon atoms,CR¹R²R³ COCHR⁸COCR⁵R⁶R⁷   (3)wherein R¹ to R³ and R⁵ to R⁸ have the same meanings as defined above.

[2] The process for preparing a β-diketone compound according to theprocess as described in [1], wherein at least one compound selected froman ester compound represented by the following formula (1), an amidetype solvent and a urea type solvent is used as a solvent,CR¹R²R³COOR⁴   (1)wherein R¹ to R³ are each independently an alkyl group of 1 to 3 carbonatoms, and R⁴ is an alkyl group.

[3] The process for preparing 2,2,6,6-tetramethyl-3,5-heptanedioneaccording to the process as described in [1], wherein the compoundrepresented by the formula (1) is a pivalic acid alkyl ester wherein R¹to R³ are each a methyl group, the compound represented by the formula(2) is pinacolone wherein R⁵ to R⁷ are each a methyl group and R⁸ ishydrogen, and the compound represented by the formula (3) is2,2,6,6-tetramethyl-3,5-heptanedione wherein R¹ to R³ and R⁵ to R⁷ areeach a methyl group and R⁸ is hydrogen.

[4] The process for preparing 2,2,6,6-tetramethyl-3,5-heptanedioneaccording to the process as described in [3], wherein the reaction iscarried out using a pivalic acid alkyl ester as a solvent and using noother solvent.

[5] The process for preparing 2,2,6,6-tetramethyl-3,5-heptanedioneaccording to the process as described in [3], wherein an amide typesolvent or a urea type solvent is used as a solvent.

[6] The process for preparing 2,2,6,6-tetramethyl-3,5-heptanedioneaccording to the process as described in [5], wherein the solvent is atleast one solvent selected from N,N-dimethylformamide,N,N-dimethylacetamide, N-methylpyrrolidone and1,3-dimethyl-2-imdazolidinone.

[7] The process for preparing 2,2,6,6-tetramethyl-3,5-heptanedioneaccording to the process as described in [6], wherein the solvent isN,N-dimethylformamide and/or 1,3-dimethyl-2-imidazolidinone.

[8] The process for preparing 2,2,6,6-tetramethyl-3,5-heptanedioneaccording to the process as described in [4], wherein the amount of thesolvent used is in the range of 3 to 30 times by mass based on thepinacolone.

[9] The process for preparing 2,2,6,6-tetramethyl-3,5-heptanedioneaccording to the process as described in [3], wherein the alkali metalof the alkali metal alkoxide catalyst is sodium or potassium.

[10] The process for preparing 2,2,6,6-tetramethyl-3,5-heptanedioneaccording to the process as described in [9], wherein the alcoholportion of the alkali metal alkoxide catalyst is a tertiary alcohol.

[11] The process for preparing 2,2,6,6-tetramethyl-3,5-heptanedioneaccording to any one of the processes as described in [3], wherein theamount of the alkali metal alkoxide catalyst used is in the range of 1to 10 times by mol based on the pinacolone.

[12] A process for preparing 2,2,6,6-tetramethyl-3,5-heptanedione,comprising the step 1 of any one of the processes as described in [3] to[11] to synthesize 2,2,6,6-tetramethyl-3,5-heptanedione by reacting thepivalic acid alkyl ester with the pinacolone in the presence of thealkali metal alkoxide catalyst and a step 2 of adding an acid to thereaction solution of 2,2,6,6-tetramethyl-3,5-heptanedione to performneutralization and adding water to the solution to separate the solutioninto two layers and thereby isolate the2,2,6,6-tetramethyl-3,5-heptanedione as an oil layer.

[13] The process for preparing 2,2,6,6-tetramethyl-3,5-heptanedioneaccording to the process as described in [12], wherein the acid is atleast one acid selected from sulfuric acid, hydrochloric acid and nitricacid.

[14] A process for preparing 2,2,6,6-tetramethyl-3,5-heptanedione,comprising recovering a pivalic acid alkyl ester, pinacolone and asolvent from the oil layer containing2,2,6,6-tetramethyl-3,5-heptanedione obtained in the process asdescribed in [12] or [13] by distillation separation and reusing them inthe reaction.

[15] A process for preparing a 2,2,6,6-tetramethyl-3,5-heptanedionemetal complex, comprising a step 3 of reacting the2,2,6,6-tetramethyl-3,5-heptanedione obtained in any one of theprocesses as described in [3] to [14] with a metal salt.

The process for preparing a 2,2,6,6-tetramethyl-3,5-heptanedione metalcomplex according to the process as described in [15], wherein the metalsalt is at least one metal salt selected from the group consisting of ahalide, a nitrate, a sulfate and a phosphate of a metal.

[17] The process for preparing a 2,2,6,6-tetramethyl-3,5-heptanedionemetal complex according to the process as described in [16], wherein themetal salt is a chloride of a metal and/or a nitrate of a metal.

[18] The process for preparing a 2,2,6,6-tetramethyl-3,5-heptanedionemetal complex according to the process as described in [15], wherein themetal of the metal salt is at least one metal selected from transitionmetals and alkaline earth metals.

[19] The process for preparing a 2,2,6,6-tetramethyl-3,5-heptanedionemetal complex according to the process as described in [18], wherein themetal is at least one metal selected from alkaline earth metals, rareearth metals, Ti, Zr, Hf and Cu.

[20] The process for preparing a 2,2,6,6-tetramethyl-3,5-heptanedionemetal complex according to the process as described in [15], wherein ahydrophilic solvent is used as a solvent in the reaction of the2,2,6,6-tetramethyl-3,5-heptanedione with the metal salt.

[21] The process for preparing a 2,2,6,6-tetramethyl-3,5-heptanedionemetal complex according to the process as described in [20], wherein thehydrophilic solvent is an alcohol of 1 to 4 carbon atoms.

[22] The process for preparing a 2,2,6,6-tetramethyl-3,5-heptanedionemetal complex according to the process as described in [21], wherein thealcohol is methanol.

[23] The process for preparing a 2,2,6,6-tetramethyl-3,5-heptanedionemetal complex according to the process as described in [15], whereinafter the reaction is completed, water is added to precipitate the2,2,6,6-tetramethyl-3,5-heptanedione metal complex, followed byisolating the metal complex.

[24] The process for preparing a 2,2,6,6-tetramethyl-3,5-heptanedionemetal complex according to the process as described in [15], wherein the2,2,6,6-tetramethyl-3,5-heptanedione metal complex is a metal complexwherein 2 to 4 molecules of 2,2,6,6-tetramethyl-3,5-heptanedione arecoordinated to 1 atom of the metal.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described in detail hereinafter.

One of the characteristic features of the present invention is toprepare a β-diketone compound represented by the following formula (3)by reacting an ester compound represented by the following formula (1)with a ketone compound represented by the following formula (2) in thepresence of an alkali metal alkoxide catalyst,CR¹R²R³COOR⁴   (1)wherein R¹ to R³ are each independently an alkyl group of 1 to 3 carbonatoms, and R⁴ is an alkyl group,CR⁵R⁶R⁷COCH₂R⁸   (2)wherein R⁵ to R⁷ are each independently an alkyl group of 1 to 3 carbonatoms, and R⁸ is hydrogen or an alkyl group of 1 to 4 carbon atoms,CR¹R²R³COCHR⁸COCR⁵R⁶R⁷   (3)wherein R¹ to R³ and R⁵ to R⁸ have the same meanings as defined above.

2,2,6,6-tetramethyl-3,5-heptanedione that is particularly useful istaken as an example of the β-diketone compound to explain the inventionin detail as below.

The preferred process of the invention is a process for preparing2,2,6,6-tetramethyl-3,5-heptanedione from a pivalic acid alkyl ester andpinacolone in an organic solvent using an alkali metal alkoxidecatalyst. The pivalic acid alkyl ester for use in the invention has astructure of the formula (1) wherein R¹ to R³ are each a methyl groupand R⁴ that is an alcohol portion of the ester is not specificallyrestricted provided that it is an alkyl group. R⁴ is preferably an alkylgroup of 1 to 6 carbon atoms. Examples of such pivalic acid alkyl estersinclude methyl pivalate, ethyl pivalate, isopropyl pivalate and butylpivalate.

When R⁴ is a phenyl group, the reactivity of the ester is per seenhanced, but since the acidity of the phenol liberated is strong, thephenol reacts with the catalyst to form an alkali metal phenoxide thatis low-alkaline, and as a result, the reaction is markedly inhibited.

The pinacolone that is a starting material is not specificallyrestricted, and any of commercially available ones is employable.

In the reaction of the invention, the reactivity greatly variesdepending upon the solvent used, and in the beginning of the reaction,the pivalic acid alkyl ester can be used as a solvent by the use of thepivalic acid alkyl ester in a large amount without using any othersolvent particularly.

When a solvent other than the pivalic acid alkyl ester is used, an amidetype solvent or a urea type solvent is preferably used because thereaction is promoted. The amide type solvent is a compound, which isliquid under the reaction conditions and has an amide bond, such asN,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc) orN-methyl-2-pyrrolidone (NMP). The urea type solvent is a compound, whichis liquid under the reaction conditions and has a urea bond, such as1,3-dimethyl-2-imidazolidinone (DMI). Particularly, DMF and DMI arepreferable because hydrogen is not present at the α-position to thecarbonyl group and any carboanion is not generated, and therefore sidereaction due to the condensation reaction of carboanion with ketone orester can be inhibited. These solvents can be used singly or as amixture of two or more kinds. It is possible to use other solvents incombination as far as no evil influence is exerted on the reaction (forexample, solvents which act on or react with the alkali metal alkoxidecatalyst cannot be used). However, if only a solvent other than theamide type or urea type solvent is used, the reactivity is markedlylowered. If the solvent used contains water, the reaction is inhibited,so that it is desirable to dehydrate the solvent prior to use.

The lower limit of the amount of the pivalic acid alkyl ester used asthe solvent or the amount of the amide type or urea type solvent is notspecifically restricted as far as stirring of the reaction system isfeasible. Although the upper limit thereof is not specificallyrestricted, too dilute reaction system lowers productivity or reactivityand is unfavorable. Therefore, the solvent is preferably used, on thebasis of mass, in an amount of 0 to 50 times by mass based on thepinacolone. The amount of the solvent is in the range of more preferably1 to 40 times by mass, particularly preferably 3 to 30 times by mass. Onthe basis of mol, the solvent is preferably used in an amount of 0 to 70times by mol based on the pinacolone. The amount of the solvent is inthe range of more preferably 0.2 to 50 times by mol, particularlypreferably 0.5 to 20 times by mol.

The amount of the pivalic acid alkyl ester used for the reaction is inthe range of 0.5 to 10 times by mol, preferably 1 to 5 times by mol,more preferably 1.1 to 3 times by mol, based on the pinacolone. If theamount of the pinacolone based on the pivalic acid alkyl ester is toolarge, the yield is lowered by the great influence of self-condensationof the pinacolone. If the amount of the pivalic acid alkyl ester basedon the pinacolone is too large, a large amount of the unreacted pivalicacid alkyl ester must be recovered. However, when the pivalic acid alkylester is used as the solvent, the pivalic acid alkyl ester used as thestarting material and the pivalic acid alkyl ester used as the solventare not differentiated in the reaction system, so that the pivalic acidalkyl ester is used in an amount of 10 to 30 times by mass based on thepinacolone.

There is no specific limitation on the method of addition of the pivalicacid alkyl ester and the pinacolone, and it is possible to feed thepinacolone previously and then add the pivalic acid alkyl ester slowlyor to add the pivalic acid alkyl ester and the pinacolone at the sametime. However, in order to prevent self-condensation of the pinacolone,it is preferable to feed the pivalic acid alkyl ester previously andthen add the pinacolone slowly so that the amount of the pivalic acidalkyl ester should exceed the amount of the pinacolone in the reactionsolution. The pivalic acid alkyl ester and the pinacolone may be addedas they are, or they may be added after dissolved in the solvent used.

The reaction temperature is desired to be in the range of 0 to 150° C.,preferably 20 to 100° C. If the reaction temperature is too low, thereactivity becomes worse and the reaction time is prolonged, resultingin low productivity. If the reaction temperature is too high, the yieldis lowered by the influences of decomposition of the solvent due toalkali and progress of side reaction.

As the alkali metal alkoxide catalyst for use in the reaction, anycompound is employable, but the alkali metal is preferably sodium orpotassium, more preferably potassium. As the alcohol for forming thealkoxide, a monohydric alcohol having an alkyl group of 1 to 6 carbonatoms which may be branched is usually used, but a polyhydric alcohol(e.g., ethylene glycol or propylene glycol) or an alkoxy alcohol whereina part of the carbon chain of the alkyl group is replaced with oxygen(e.g., monoalkyl ether of ethylene glycol) may be used. Preferable is atertiary alcohol having an alkyl group. For example,tert-butoxypotassium can be mentioned.

The alkali metal alkoxide catalysts mentioned above may be used singlyor in combination of two or more kinds in an arbitrary proportion. Ifthe amount of the base added is too small, the reactivity becomes worse.If the amount thereof is too large, the yield is lowered bydecomposition of the solvent due to alkali or side reaction. The amountof the base is preferably in the range of 1 to 10 mol based on 1 mol ofthe pinacolone.

When Claisen condensation reaction of the pivalic acid alkyl ester withthe pinacolone is carried out in the presence of the alkali metalalkoxide catalyst to synthesize 2,2,6,6-tetramethyl-3,5-heptanedione,the resulting 2,2,6,6-tetramethyl-3,5-heptanedione is present as analkyl metal salt. In order to isolate the2,2,6,6-tetramethyl-3,5-heptanedione, the alkali metal salt of2,2,6,6-tetramethyl-3,5-heptanedione is neutralized with an acid andthereby freed.

Examples of the acids used herein include mineral acids, such ashydrochloric acid, sulfuric acid, nitric acid and phosphoric acid;organic acids, such as formic acid and acetic acid; and Lewis acids,such as ferrous chloride, ferric chloride, stannous chloride andaluminum chloride. Preferably used are sulfuric acid, hydrochloric acidand nitric acid. These acid components may be used singly or incombination of two or more kinds in an arbitrary proportion. The amountof the acid added is sufficient to be not less than the equivalentamount of the alkali metal alkoxide catalyst used for the reaction.Since heat generation takes place in the neutralization, cooling may becarried out if necessary.

In order to recover the 2,2,6,6-tetramethyl-3,5-heptanedione formed bythe reaction, water is added to the reaction solution to separate thesolution into an oil layer consisting of the2,2,6,6-tetramethyl-3,5-heptanedione formed by the reaction, a pivalicacid alkyl ester, pinacolone and a solvent, and an aqueous layerconsisting of water, a solvent and an inorganic salt. Since the2,2,6,6-tetramethyl-3,5-heptanedione has bulky hydrophobic groups, it ishardly dissolved in water, so that the2,2,6,6-tetramethyl-3,5-heptanedione can be recovered in a good recoveryratio even if no extraction agent is used. However, hydrocarbon, ether,aromatic hydrocarbon or the like may be added for the extraction whenneeded.

The oil layer separated as above can be subjected to distillationpurification when needed. The pivalic acid alkyl ester, pinacolone andthe solvent having a lower boiling point than the aimed product can bereadily recovered and reused for the reaction.

There is no specific limitation on the process to prepare a metalcomplex from the 2,2,6,6-tetramethyl-3,5-heptanedione prepared by theprocess of the invention. For example, the metal complex can be preparedby the processes described in Inorganic Synthesis, 11 (1968) andInorganic Synthesis, 31 (1997). Usually, the metal complex can beprepared by reacting the 2,2,6,6-tetramethyl-3,5-heptanedione with ametal salt in an organic solvent.

The metal of the 2,2,6,6-tetramethyl-3,5-heptanedione metal complex isnot specifically restricted provided that it is a metal capable offorming a metal complex together with β-diketone. Preferred examples ofsuch metals include alkaline earth metals, rare earth metals, Ti, Zr, Hfand Cu. Examples of the alkaline earth metals include Sr and Ba, andexamples of the rare earth metals include Y, La, Pr, Nd, Sm, Eu, Tm andTb.

The metal is preferably a metal being divalent to tetravalent ions inconsideration of the number being molecules of the2,2,6,6-tetramethyl-3,5-heptanedione readily coordinated. When the metalion is n-valent, n molecules of the 2,2,6,6-tetramethyl-3,5-heptanedioneare usually coordinated to one metal.

Although the metal salt used for the reaction with the2,2,6,6-tetramethyl-3,5-heptanedione is not specifically restricted,preferable is a salt of inorganic ion. Examples of such salts includehalide, nitrate, sulfate, phosphate and perchlorate. Particularlypreferable are nitrate and chloride. These salts may be used singly oras a mixture.

The quantity ratio between the metal salt and the2,2,6,6-tetramethyl-3,5-heptanedione varies depending upon the valenceof the metal of the metal salt, but when the valence of the metal is n,it is preferable to use the 2,2,6,6-tetramethyl-3,5-heptanedione in anamount of n×0.9 to n×1.5 times by mol.

As the solvent for the reaction of the2,2,6,6-tetramethyl-3,5-heptanedione with the metal salt, an organicsolvent can be used without any restriction. The solvent is preferably asolvent capable of dissolving the metal salt. Therefore, preferable is apolar solvent, particularly a hydrophilic solvent, and more preferableis an alcohol type solvent having 1 to 4 carbon atoms. Examples of suchsolvents include methanol, ethanol, propanol, isopropanol, butanol,methoxyethanol and ethoxyethanol.

The reaction temperature is not lower than the melting point of thesolvent and not higher than the boiling point thereof. When the reactionis carried out at a temperature in the vicinity of room temperature, anytrouble is not brought about. Accordingly, the reaction temperature isin the range of preferably 10 to 40° C., particularly preferably 15 to30° C.

When the solvent is hydrophobic, the2,2,6,6-tetramethyl-3,5-heptanedione metal complex formed by thereaction can be obtained by concentration. When the solvent is ahydrophilic solvent that is usually used, water is added to precipitatethe metal complex as solids, and the solids can be isolated byfiltration, centrifugation or the like. Depending upon the type of themetal, the metal complex is sometimes precipitated even if water is notparticularly added.

The 2,2,6,6-tetramethyl-3,5-heptanedione metal complex can be convertedinto a metal oxide by the chemical vapor deposition publicly known(e.g., the 4th edition Experimental Chemistry Lectures 13, p. 46). Forexample, the 2,2,6,6-tetramethyl-3,5-heptanedione metal complex isevaporated to give vapor, and the vapor is mixed with a gas containingoxygen and heated to obtain a metal oxide.

A typical example of such process is MOCVD. MOCVD is a general name oftechnique wherein an organometallic compound used as a starting materialis thermally decomposed in the vicinity of a substrate to performcrystal growth, and this technique is now utilized for the formation ofoxides such as compound semiconductor, magnetic substance, ferroelectricthin film and high-temperature superconductor crystal. Morespecifically, the substrate is heated in a vacuum reactor, then to thevicinity of the substrate, an organometallic compound gas and if desiredoxygen are fed, and thermal decomposition reaction is conducted on thesubstrate surface or in the vicinity of the substrate by inductionheating due to high-frequency power or plasma generation to form a metalfilm or an oxide film on the substrate surface.

It is known that the β-diketone metal complex or its derivative is usedas the organometallic compound that is a starting material in MOCVD, andthe decomposability of the organometallic compound or the evaporationtemperature can be controlled by appropriately selecting the hydrocarbongroup of the side chain of the β-diketone that is a ligand.

EXAMPLE

The present invention is further described with reference to thefollowing examples, but it should be construed that the invention is inno way limited to those examples.

Quantitative determination of 2,2,6,6-tetramethyl-3,5-heptanedione inthe following examples was made by gas chromatography. The analyticalconditions are described below. With regard to the2,2,6,6-tetramethyl-3,5-heptanedione, a reagent having a purity of notless than 95% available from Wako Junyaku K.K. was used as a standardproduct of 95% purity.

Gas Chromatography Conditions

Apparatus: GC-14A manufactured by Shimadzu Seisakusho K.K., Split method(Split Ratio: 60)

Capillary Column: DB-5 manufactured by J&W Co., 0.25 mmø×30 m,stationary liquid thickness: 0.25μ

Carrier gas: helium

Injection quantity: 1 μl

INJ. temperature: 250° C.

DET. temperature (FID): 280° C.

Temperature program: 50° C. →5 min, hold →10° C./min, heating up to 250°C.

Quantitative determination method: internal standard method (internalstandard substance: naphthalene)

Example 1

In a 2-liter four-necked flask, 1000 g of DMF and 135 g oftert-butoxypotassium were placed, and they were heated up to 50° C. withstirring by a mechanical stirrer. Then, 186 g of methyl pivalate wasadded by a dropping funnel. Thereafter, a mixed solution of 80 g ofpinacolone and 100 g of DMF was added by a dropping funnel over a periodof 3 hours, followed by further stirring for 5 hours under heating. Itwas confirmed by gas chromatography that2,2,6,6-tetramethyl-3,5-heptanedione was produced in an amount of 76.5 g(yield: 52% (based on pinacolone)) in the solution.

Example 2

The reaction was carried out in the same manner as in Example 1, exceptthat the solvent was changed to DMAc. It was confirmed by gaschromatography that 2,2,6,6-tetramethyl-3,5-heptanedione was produced inan amount of 47.1 g(yield: 32% (based on pinacolone)) in the solution.

Example 3

The reaction was carried out in the same manner as in Example 1, exceptthat the solvent was changed to DMI. It was confirmed by gaschromatography that 2,2,6,6-tetramethyl-3,5-heptanedione was produced inan amount of 88.3 g (yield: 60% (based on pinacolone)) in the solution.

Example 4

The reaction was carried out in the same manner as in Example 1, exceptthat the solvent was changed to NMP. It was confirmed by gaschromatography that 2,2,6,6-tetramethyl-3,5-heptanedione was produced inan amount of 58.9 g (yield: 40% (based on pinacolone)) in the solution.

Example 5

The reaction was carried out in the same manner as in Example 1, exceptthat the amount of tert-butoxypotassium was changed to 270 g. It wasconfirmed by gas chromatography that2,2,6,6-tetramethyl-3,5-heptanedione was produced in an amount of 103.0g (yield: 70% (based on pinacolone)) in the solution.

Example 6

The reaction was carried out in the same manner as in Example 1, exceptthat tert-butoxypotassium was replaced with 81.6 g of sodium ethoxide.It was confirmed by gas chromatography that2,2,6,6-tetramethyl-3,5-heptanedione was produced in an amount of 22.1 g(yield: 15% (based on pinacolone)) in the solution.

Example 7

The reaction was carried out in the same manner as in Example 1, exceptthat tert-butoxypotassium was replaced with 115.2 g oftert-butoxysodium. It was confirmed by gas chromatography that2,2,6,6-tetramethyl-3,5-heptanedione was produced in an amount of 61.8 g(yield: 42% (based on pinacolone)) in the solution.

Example 8

The reaction was carried out in the same manner as in Example 1, exceptthat the reaction temperature was changed to 90° C. It was confirmed bygas chromatography that 2,2,6,6-tetramethyl-3,5-heptanedione wasproduced in an amount of 66.2 g (yield: 45% (based on pinacolone)) inthe solution.

Example 9

The reaction was carried out in the same manner as in Example 1, exceptthat any particular solvent is not used but methyl pivalate was used inthe same amount as that of DMF. It was confirmed by gas chromatographythat 2,2,6,6-tetramethyl-3,5-heptanedione was produced in an amount of44.2 g (yield: 30% (based on pinacolone)) in the solution.

Reference Example 1

The reaction was carried out in the same manner as in Example 1, exceptthat the solvent was changed to 1,4-dioxane. As a result, the yield was1% (based on pinacolone).

Reference Example 2

The reaction was carried out in the same manner as in Example 1, exceptthat the solvent was changed to acetonitrile. As a result,2,2,6,6-tetramethyl-3,5-heptanedione was hardly produced.

Reference Example 3

The reaction was carried out in the same manner as in Example 1, exceptthat the solvent was changed to tert-butyl methyl ether. As a result,the yield was 2% (based on pinacolone).

Reference Example 4

The reaction was carried out in the same manner as in Example 1, exceptthat the solvent was changed to toluene. As a result, the yield was 4%(based on pinacolone).

Reference Example 5

The reaction was carried out in the same manner as in Example 1, exceptthat the solvent was changed to tert-butanol. As a result,2,2,6,6-tetramethyl-3,5-heptanedione was hardly produced.

Reference Example 6

The reaction was carried out in the same manner as in Example 1, exceptthat the solvent was changed to dimethyl sulfoxide. As a result, theyield was 10% (based on pinacolone).

Reference Example 7

The operations of Example 1 were carried out using dichloromethane as asolvent. As a result, heat generation took place in the stage of mixingdichlormethane with tert-butoxypotassium, and the desired reaction didnot proceed.

Reference Example 8

The reaction was carried out in the same manner as in Example 7, exceptthat the solvent was changed to xylene. As a result,2,2,6,6-tetramethyl-3,5-heptanedione was hardly produced.

Comparative Example 1

The reaction was carried out in the same manner as in Example 1, exceptthat methyl pivalate was replaced with phenyl pivalate. As a result,2,2,6,6-tetramethyl-3,5-heptanedione was not produced.

Example 10

To the reaction solution containing2,2,6,6-tetramethyl-3,5-heptanedione, said reaction solution having beensynthesized in the same manner as in Example 1, 74.3 g of sulfuric acidwas added and then 1000 g of water was further added, to separate thesolution into two layers of an oil layer and an aqueous layer. The oillayer was recovered and analyzed by GC. As a result, the recovery of2,2,6,6-tetramethyl-3,5-heptanedione was 99.5%.

Example 11

In 1155 g of methanol, 40.4 g (1.01 mol) of NaOH of 96% purity wasdissolved with stirring, and the resulting solution was cooled to roomtemperature. Then, 180.3 g (0.882 mol) of2,2,6,6-tetramethyl-3,5-heptanedione of 90% purity was added little bylittle. To the mixture, a solution obtained by dissolving 132 g (0.294mol) of Y(NO₃)₃.6H₂O of 85.6% purity in 1225 g of methanol was added ata temperature of 25 to 28° C. over a period of 30 minutes. The reactionwas conducted for 1 hour, and the crystals precipitated were filteredoff. To the resulting solution, 3500 g of water was dropwise added overa period of 1 hour and 30 minutes. After the dropwise addition wascompleted, stirring was performed for 1 hour. The resulting crystalswere taken out by centrifugation and then dried. Thus, 166.8 g (yield:89%) of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)yttrium wasobtained.

Example 12

In 256 g of methanol, 48.6 g (0.252 mol) of a sodium methylate methanolsolution of 28% purity was dissolved, and the resulting solution wascooled to room temperature. Then, 49.3 g (0.252 mol) of2,2,6,6-tetramethyl-3,5-heptanedione of 94% purity was dropwise addedwith stirring. To the mixture, a solution obtained by dissolving 45.8 g(0.084 mol) of Eu(NO₃)₃.6H₂O of 81.9% purity in 367 g of methanol wasadded at a temperature of 25 to 28° C. over a period of 30 minutes. Thereaction was conducted for 1 hour, and the crystals precipitated-werefiltered off. To the resulting solution, 1000 g of water was dropwiseadded over a period of 1 hour and 30 minutes. After the dropwiseaddition was completed, stirring was performed for 1 hour. The resultingcrystals were taken out by centrifugation and then dried. Thus, 55.2 g(yield: 93.6%) of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)europiumwas obtained.

Example 13

55.2 g (yield: 93.6%) oftris(2,2,6,6-tetramethyl-3,5-heptanedionato)terbium was obtained in thesame manner as in Example 12, except that 49.3 g (0.252 mol) of2,2,6,6-tetramethyl-3,5-heptanedione of 94% purity was used as2,2,6,6-tetramethyl-3,5-heptanedione and 46.0 g (0.084 mol) ofTb(NO₃)₃.6H₂O of 82.7% purity was used instead of Eu(NO₃)₃.6H₂O.

Example 14

To 177 g of methanol, 43.7 g (0.216 mol) of2,2,6,6-tetramethyl-3,5-heptanedione of 91% purity was dropwise addedwith stirring. To the resulting solution, a solution, which had beenobtained by dissolving 12.7 g (0.054 mol) of ZrCl₄ of 99% purity in 218g of methanol and cooled to room temperature, was added over a period ofabout 5 minutes. The reaction was conducted for 1 hour with stirring,and 590 g of water was added over a period of 50 minutes. Then, stirringwas performed for 1 hour. The resulting solution was adjusted to pH 6.6with a 20% NaOH solution. The resulting crystals were collected bycentrifugation and then dried. Thus, 43.9 g (yield: 98.2%) oftetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)zirconium was obtained.

Example 15

In 67 g of methanol, 6.6 g (0.0366 mol) of a sodium methylate methanolsolution of 30% purity was dissolved, and the resulting solution wascooled to room temperature. Then, 7.41 g (0.0366 mol) of2,2,6,6-tetramethyl-3,5-heptanedione of 91% purity was dropwise addedwith stirring. To the mixture, a solution obtained by dissolving 4.83 g(0.0183 mol) of Ba(NO₃)₂ of 99% purity in 38 g of water was added. Thereaction was conducted for 1 hour, and 100 g of water was dropwiseadded. After the dropwise addition was completed, stirring was performedfor 1 hour. The resulting crystals were taken out by centrifugation andthen dried. Thus, 8.07 g (yield: 87.6%) ofbis(2,2,6,6-tetramethyl-3,5-heptanedionato)barium was obtained.

Example 16

7.28 g (yield: 87.7%) ofbis(2,2,6,6-tetramethyl-3,5-heptanedionato)strontium was obtained in thesame manner as in Example 15, except that 3.87 g of Sr(NO₃)₂ of 99.5%purity was used instead of Ba(NO₃)₂.

Example 17

In 53.2 g of methanol, 9.31 g (0.0517 mol) of a sodium methylatemethanol solution of 30% purity was dissolved, and the resultingsolution was cooled to room temperature. Then, 10.5 g (0.0517 mol) of2,2,6,6-tetramethyl-3,5-heptanedione of 91% purity was dropwise addedwith stirring. Then, 6.46 g (0.0259 mol) of Cu(NO₃)₂.6H₂O was added. Thereaction was conducted for 1 hour, and the crystals precipitated werecollected by filtration. The crystals were dissolved in 100 g of diethylether, washed 5 times with 100 g of water and then evaporated to dry.Thus, 8.74 g (yield: 78.7%) ofbis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper was obtained.

EFFECT OF THE INVENTION

According to the present invention, it becomes possible to use as acatalyst an alkali metal alkoxide that is easy to handle, and2,2,6,6-tetramethyl-3,5-heptanedione can be prepared under mildconditions at a low cost without necessity to invest a large sum ofmoney in plant and equipment.

The 2,2,6,6-tetramethyl-3,5-heptanedione prepared by the invention canbe coordinated to a metal to synthesize a complex, and hence a2,2,6,6-tetramethyl-3,5-heptanedione metal complex that is a startingmaterial of MOCVD can be provided at a low cost.

1. A process for preparing a β-diketone compound represented by thefollowing formula (3), comprising a step 1 of reacting an ester compoundrepresented by the following formula (1) with a ketone compoundrepresented by the following formula (2) in the presence of an alkalimetal alkoxide catalyst,CR¹R²R³COOR⁴   (1) wherein R¹ to R³ are each independently an alkylgroup of 1 to 3 carbon atoms, and R⁴ is an alkyl group,CR⁵R⁶R⁷COCH₂R⁸   (2) wherein R⁵ to R⁷ are each independently an alkylgroup of 1 to 3 carbon atoms, and R⁸ is hydrogen or an alkyl group of 1to 4 carbon atoms,CR¹R²R³COCHR⁸COCR⁵R⁶R⁷   (3) wherein R¹ to R³ and R⁵ to R⁸ have the samemeanings as defined above.
 2. The process for preparing a β-diketonecompound as claimed in claim 1, wherein at least one compound selectedfrom an ester compound represented by the following formula (1), anamide type solvent and a urea type solvent is used as a solvent,CR¹R²R³COOR⁴   (1) wherein R¹ to R³ are each independently an alkylgroup of 1 to 3 carbon atoms, and R⁴ is an alkyl group.
 3. The processfor preparing 2,2,6,6-tetramethyl-3,5-heptanedione as claimed in claim1, wherein the compound represented by the formula (1) is a pivalic acidalkyl ester wherein R¹ to R³ are each a methyl group, the compoundrepresented by the formula (2) is pinacolone wherein R⁵ to R⁷ are each amethyl group and R⁸ is hydrogen, and the compound represented by theformula (3) is 2,2,6,6-tetramethyl-3,5-heptanedione wherein R¹ to R³ andR⁵ to R⁷ are each a methyl group and R⁸ is hydrogen.
 4. The process forpreparing 2,2,6,6-tetramethyl-3,5-heptanedione as claimed in claim 3,wherein the reaction is carried out using a pivalic acid alkyl ester asa solvent and using no other solvent.
 5. The process for preparing2,2,6,6-tetramethyl-3,5-heptanedione as claimed in claim 3, wherein anamide type solvent or a urea type solvent is used as a solvent.
 6. Theprocess for preparing 2,2,6,6-tetramethyl-3,5-heptanedione as claimed inclaim 5, wherein the solvent is at least one solvent selected fromN,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and1,3-dimethyl-2-imdazolidinone.
 7. The process for preparing2,2,6,6-tetramethyl-3,5-heptanedione as claimed in claim 6, wherein thesolvent is N,N-dimethylformamide and/or 1,3-dimethyl-2-imidazolidinone.8. The process for preparing 2,2,6,6-tetramethyl-3,5-heptanedione asclaimed in claim 4, wherein the amount of the solvent used is in therange of 3 to 30 times by mass based on the pinacolone.
 9. The processfor preparing 2,2,6,6-tetramethyl-3,5-heptanedione as claimed in claim3, wherein the alkali metal of the alkali metal alkoxide catalyst issodium or potassium.
 10. The process for preparing2,2,6,6-tetramethyl-3,5-heptanedione as claimed in claim 9, wherein thealcohol portion of the alkali metal alkoxide catalyst is a tertiaryalcohol.
 11. The process for preparing2,2,6,6-tetramethyl-3,5-heptanedione as claimed in claim 3, wherein theamount of the alkali metal alkoxide catalyst used is in the range of 1to 10 times by mol based on the pinacolone.
 12. A process for preparing2,2,6,6-tetramethyl-3,5-heptanedione, comprising the step 1 of any oneof claims 3 to 11 to synthesize 2,2,6,6-tetramethyl-3,5-heptanedione byreacting the pivalic acid alkyl ester with the pinacolone in thepresence of the alkali metal alkoxide catalyst and a step 2 of adding anacid to the reaction solution of 2,2,6,6-tetramethyl-3,5-heptanedione toperform neutralization and adding water to the solution to separate thesolution into two layers and thereby isolate the2,2,6,6-tetramethyl-3,5-heptanedione as an oil layer.
 13. The processfor preparing 2,2,6,6-tetramethyl-3,5-heptanedione as claimed in claim12, wherein the acid is at least one acid selected from sulfuric acid,hydrochloric acid and nitric acid.
 14. A process for preparing2,2,6,6-tetramethyl-3,5-heptanedione, comprising recovering a pivalicacid alkyl ester, pinacolone and a solvent from the oil layer containing2,2,6,6-tetramethyl-3,5-heptanedione obtained in the process of claim 12or 13 by distillation separation and reusing them in the reaction.
 15. Aprocess for preparing a 2,2,6,6-tetramethyl-3,5-heptanedione metalcomplex, comprising a step 3 of reacting the2,2,6,6-tetramethyl-3,5-heptanedione obtained in the process of any oneof claims 3 to 14 with a metal salt.
 16. The process for preparing a2,2,6,6-tetramethyl-3,5-heptanedione metal complex as claimed in claim15, wherein the metal salt is at least one metal salt selected from thegroup consisting of a halide, a nitrate, a sulfate and a phosphate of ametal.
 17. The process for preparing a2,2,6,6-tetramethyl-3,5-heptanedione metal complex as claimed in claim16, wherein the metal salt is a chloride of a metal and/or a nitrate ofa metal.
 18. The process for preparing a2,2,6,6-tetramethyl-3,5-heptanedione metal complex as claimed in claim15, wherein the metal of the metal salt is at least one metal selectedfrom transition metals and alkaline earth metals.
 19. The process forpreparing a 2,2,6,6-tetramethyl-3,5-heptanedione metal complex asclaimed in claim 18, wherein the metal is at least one metal selectedfrom alkaline earth metals, rare earth metals, Ti, Zr, Hf and Cu. 20.The process for preparing a 2,2,6,6-tetramethyl-3,5-heptanedione metalcomplex as claimed in claim 15, wherein a hydrophilic solvent is used asa solvent in the reaction of the 2,2,6,6-tetramethyl-3,5-heptanedionewith the metal salt.
 21. The process for preparing a2,2,6,6-tetramethyl-3,5-heptanedione metal complex as claimed in claim20, wherein the hydrophilic solvent is an alcohol of 1 to 4 carbonatoms.
 22. The process for preparing a2,2,6,6-tetramethyl-3,5-heptanedione metal complex as claimed in claim21, wherein the alcohol is methanol.
 23. The process for preparing a2,2,6,6-tetramethyl-3,5-heptanedione metal complex as claimed in claim15, wherein after the reaction is completed, water is added toprecipitate the 2,2,6,6-tetramethyl-3,5-heptanedione metal complex,followed by isolating the metal complex.
 24. The process for preparing a2,2,6,6-tetramethyl-3,5-heptanedione metal complex as claimed in claim15, wherein the 2,2,6,6-tetramethyl-3,5-heptanedione metal complex is ametal complex wherein 2 to 4 molecules of2,2,6,6-tetramethyl-3,5-heptanedione are coordinated to 1 atom of themetal.